ADAPTATION TO HABITATS. Lecture Objectives. Introduction

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1 ADAPTATION TO HABITATS Lecture Objectives 1. Define ecology and the related terms discussed. 2. Build a simple food web using only insects for the primary, secondary and tertiary trophic levels. 3. Describe the ways insects have adapted to the soil and aquatic environments. 4. Discuss the advantages of biological monitoring and the specific indications of poor water quality. 1 2 Introduction Are you ready for an adventure? We are now going to take a journey to some specialized habitats where insects have become very successful. In unit 3, you learned of some of the adaptations such as gills for breathing underwater, and in lab you learned of various leg adaptations for digging in soil. Now we are going to explore some of the specific habitats where these adaptations, and others, are useful. Before we begin the lecture, please read the text chapter on aquatic insects, pages , and 260 and the chapter on soil insects pages and 233. Terms and Concepts Ecology - The study of the interactions between organisms and their environment. Environment - The environment is the physical world that affects the life of an individual, population or community. It is composed of two parts, the Biotic which includes all living organisms such as plants, animals and microbes, and the Abiotic or non-living factors such as temperature, light, water, and nutrients. Habitat: A habitat is the locality or site and type of environment that an organism lives on or in. A pond, field or oak tree are all examples of habitats. Niche: A niche is the ecological role a species plays in a community such as an insect that feeds on root of grasses or one that eats aphids on leaves. It is what an organism does for a living within a habitat. Population: A population is a group of individual organisms that belong to the same species and live in a particular geographic location. Community: A community is all the organisms living in a particular area and includes populations of different species of plants and animals. 3 Read textbook pages , and 260, and and 233. Ecosystem: An ecosystem is the combination of the community of organisms in 4an area and the abiotic factors such as the air, water and soil. Biological Monitoring One important way insects are being used by humans is to determine the relative health or level of pollution in aquatic habitats. This is done by sampling the insects in a lake or stream and measuring the number of individual insects, and most importantly, the number of species. The results are then compared with those from samples taken in other lakes or different portions of the stream. Some insects are very hardy and will be found in almost any quality of water samples. Others, however, are much more sensitive and are found only in unpolluted water. A healthy lake or stream will have a wide variety of species (including those sensitive to pollution) while a polluted stream will have only a few hardy species though they may be present in large numbers. If you find very few sensitive species and many pollution tolerant species, that usually means there is pollution in the water. Water Quality Traditionally, water quality has been tested in the laboratory by measuring the chemicals found in the water. This method is popular because it is quick and easy to do. One problem with these kinds of tests though, is that the sample may be taken on a day when the factory or pollution source is not releasing any chemicals so none will show up on the tests. Another is the difficultly knowing which chemicals to test for or what effect the interaction of the different chemicals present may have on living organisms. Biological monitoring has an advantage over chemical tests because you can collect the sample at any time and still get a reliable water quality reading. This is because the insects are constantly sampling the water over long periods of time. If you take a sample on a day when the factory or pollution source is not releasing chemicals, the insects you will find in the water will not be different than the insects you would find on a day the factory was not releasing chemicals. When taking water samples for water quality tests, you usually take a sample above the factory, or other potential pollution source, and one below the factory. You then compare the results. If you have a lot of sensitive species at sample site 1, and very few at Sample site 2, then the source of pollution may be the factory. However, if you found the same numbers of species at both sites 1 and 2 then you would assume the factory is not contributing significant amounts of pollution

2 Water Quality Indicators Aquatic Habitats There are different kinds of aquatic habitats, and with each habitat comes different insect fauna and different functional feeding groups. The aquatic habitats we will discuss include: Lentic (ponds and lakes) - standing water Lotic (streams and rivers) - running water Marine (inter-tidal and littoral) Temporary bodies of water puddles, crab-holes, tree holes When sampling there are several common indicators to consider. Mayflies indicate an increase in particulate matter. Bloodworms (Chironomidae) increase when oxygen levels drop. Plecoptera decline as water temperature increases. Many species disappear with pesticide run-off. There will be an abundance of only a few species with eutrophication (abundance of organic matter). Important factors when considering aquatic habitats include: water speed, water temperature, and dissolved solvents. 7 8 Functional Feeding Groups Shredders - feed on living or decomposing plant tissues, including wood which they chew, mine or gouge. (water boatman) Insects and the Aquatic Environment Collectors - feed on fine particulate matter by filtering particles from aqueous suspension. (black fly larvae) Scrapers - feed on attached algae and diatoms by grazing solid surfaces. (dytiscid water beetles) Piercers - feed on cell and tissue fluids from vascular plants of larger algae by piercing the cell wall and sucking out the contents. Predators - feed on living animal tissue. (Helgrammites, Megaloptera,-only found in clean waters.) Parasites - feed on living animal tissue as external or internal parasites of Take a close look at the drawing of the stream in front of you. Below the stream any stage of another organism. are enlarged pictures of insects with lines indicating where they would be found in the stream. Think about where in the stream the different insects are located. Is Scavengers feed on dead plant or animal materials (detritus). (water the water moving fast or slow, is it deep or shallow, is it rocky or muddy? On the striders) next few slides we will discuss the location of these insects in the aquatic habitat. See if you can fit the examples from the following diagram to their correct functional feeding groups. 9 You may want to refer back to this diagram from time to time. 10 Aquatic insects Lets start with the mosquito larvae at the left side of drawing on the previous slide. Notice that it is found in the quiet part of stream and that it is near the surface of the water. This mosquito larvae represents a number of insects that hang from the surface tension of the water as though they were hanging from the ceiling. They do this so that they can remain near the surface and breath through their snorkel-like tail that has a spiracle opening in the end. They hang from the surface using a special ring of hairs that surround spiracle. These hairs extend out over the surface of the water like grappling hooks. The hairs, spiracle opening, and trachea are all hydrofuge structures. This means that they are water repellant. Aquatic Insects - continued Look now at the damselfly. This insect represents predacious aquatic insects that sit quietly and grab prey when it swims by. It also represents insects that have developed gills (the leaf-like tail structures) to help them breath underwater. They use their gills for cutaneous gas exchange. Next is the water strider. The water strider represents those insects that live on the water surface supported by the surface tension. These insects also have hydrofuge structures, in this case their long legs and tarsi. Water striders (Gerridae) are also scavengers of dead and dying insects that fall on the water surface. Water boatmen represent those insects that are simply good swimmers. They graze on aquatic plants near the bottom of the stream or pond. The water boatman also represents those insects that carry air with them from the surface. This air can either be carried as film or bubble, plastron, on the outside of the body or between the wings and abdomen. As the oxygen is sucked out of the bubble of air the ratio of nitrogen in the bubble in increases causing the bubble to absorb oxygen from the water. This gas exchange increases the amount of time the insect can stay underwater. crabhole mosquito larvae 11 Hemiptera: Corixidae (water boatman) 12 2

3 Aquatic Insects - continued Video Brine Flies The mayfly larvae illustrated in the diagram is a type that burrows in the mud at the bottom of lakes and slow moving streams and rivers. They eat small food particles that float past in the water. The caddisfly larvae illustrated is one that builds a case or home for itself out of rocks or other debris. It feeds by grazing on the algae or other plant matter on the bottom of the water. Other caddisfly larvae actually spin a web between rocks on the stream bottom in which they catch small food particles. The Stonefly is an example of an insect that is adapted to living in strong current by having an extremely flattened body and strong grasping legs. It feeds on other insects or on pieces of dead leaves in the water. 13 IMPORTANT NOTE: Throughout the course units, you will be asked to view short video clips. Please understand that many of these video clips are copyrighted and are NOT to be used outside of this class and only may be used for this semester. Please do not copy or distribute these clips. 14 Soil Habitats Many if not most insects spend at least part of their life in or on the soil environment. Most only spend the egg, larval, or pupal stage there with the pupal stage being the most common. Advantages of living in the soil include a constant and moderated temperature that is cooler than the outside air in the summer and warmer in the winter. The air down in the soil is also very humid which most insects prefer. The soil also provides concealment and protection for vulnerable eggs, larvae and pupae. Soil Profile Look closely at the illustration of the insects found in a profile of soil. Notice the general appearance of the insects, their appendages, color and body shape Soil Insects The insects at the top of the illustration are those that live both above and below the soil surface, and often inhabit any leaf litter that might be present. These insects in general have good vision, pigmented bodies, and long appendages. As you move down deeper in the soil profile, a trend in the appearance of the insects becomes apparent. The length and size of appendages is reduced, pigmentation of the body is lost, the bodies are less scleritized, and eyes are reduced or completely absent. Recycling Nutrients Dung Beetles Insects are great at recycling nutrients in the soil. Below is a diagram of how a dung beetle recycles nutrients. A dung beetle will live below a dung pad (usually a cow pie) and make burrows into the soil. She forms the dung into balls (called dung bells) that she will pull down into her burrows. Within these dung bells she will lay eggs. As the eggs hatch, the larva will feed on the nutrient-rich dung. Because of her dung bells, the dung beetle helps to put nutrients back into the soil and she also helps to aerate the soil. Other less obvious adaptations include rings of short spines around the body that help legless insects undulate forward through the soil. dung beetle on dung ball Thought Question: June beetle grub Many insects that live their entire lives in the soil are very small. Why do you think being small would be an advantage in the soil? This is only a thought question and does not have to go in the journal

4 Recycling Nutrients Leafcutter Ants Video Leafcutter Ants Ants help the environment as well because they often form intricate burrows beneath the earth's surface--these help aerate the soil. Many of you may have watched ants pull all sorts of food into their nests. Often ants will carry seeds, pieces of leaves, and other organic material into their underground homes. In so doing, the soil is enriched with the organic material and the ants are fed. Leafcutter ants are famous for doing this. Each leafcutter ant will clip a large portion of a leaf with its powerful jaws, carry the leafcut to the nest, where the leafcuts are used to grow a fungus the ant harvests for food. 19 IMPORTANT NOTE: Throughout the course units, you will be asked to view short video clips. Please understand that many of these video clips are copyrighted and are NOT to be used outside of this class and only may be used for this semester. Please do not copy or distribute these clips. 20 Food Webs This is a diagram of a Food Web. A food web represents the path that food (energy) takes as it passes through a community of organisms. This energy is passed on when an organism is eaten by another organism as indicated by the arrows. Written to the right side of the food web are the labels indicating different trophic levels. These trophic levels represent how many organisms the food energy has passed through. Food Webs At the bottom of the food web is the producer trophic level. These are the plants that actually make (produce) the food out of energy from the sun, soil nutrients, and carbon dioxide, that will be used by all the other organisms. The next trophic level is the primary consumers. As the name indicates these are the animals that consume (eat) the producers. Included in this level are all the herbivorous (plant eating) animals from grasshoppers to cows. On the third level are the secondary consumers which feed on primary consumers. Examples include a wolf eating a deer, us eating a steak or a praying mantis eating a grasshopper. If you look closely, you will see that things start to get complicated at the this level because two of the secondary consumers are shown to feed on plants directly(as indicated by the cream colored arrows). This shows that the trophic level an organism represents is solely dependant on what it eats. For example, the mouse on the secondary consumer level is placed there because it is eating a grasshopper. However, the cream colored arrow shows that it can also act as a primary consumer when it eats plants (probably seeds) directly. Because many organisms eat a variety of foods, food webs can be extremely complicated Assignment non-graded Draw a food web similar to the one previously described substituting insects for the non-insects (except, of course, the producers). The food web you produce does not need to be as extensive as the previous one, but should include at least eight different kinds of insects and extend to the tertiary consumer level. You can either draw the insects, use clipart of insects, or simply write the name of the insect. Be sure to be fairly specific (family level if possible) when describing your insect. Do not just say beetle or fly. Remember, it is important to know exactly what the insect is feeding on because they can fit on different levels depending on their diet. You don't need to turn in this assignment (unless you want some feedback on it). However, you will want to complete it now since there may be a question on the next exam that will require you to have thought through this. You may even have to make a food web containing insects for the exam. Contact me if you have any problems. 23 Transfer of Energy To the right is a figure depicting the amount of energy that is actually converted into new biomass (organisms) in each successive trophic level. The numbers at the right indicate the number of Joules (J) of energy contained in the bodies of the organisms at that level. In this figure there are 10,000 J of energy stored in the body of the plants at the producer level. If the primary consumers were to eat 10,000 J worth of plants only 1,000 J worth of that energy would actually be turned into grasshopper bodies. The rest would be either burned as energy or simply passed on as excrement. The same amount of loss would occur on average at the next two levels which is why a field can support more mice than snakes. This is called the general rule of 10's since on average only 10% of the energy is transferred from one trophic level to the next. Thought Question: If you were the leader of a food starved nation and had to chose to use land for grain or beef production which would chose and why? This is not a journal entry. 24 4

5 Conclusion Ok, we covered a lot of ground in this unit and hopefully your head is above water. (I couldn t resist the pun.) Make sure to review the terms given in this lecture and be able to create a food web with the different trophic levels. Also be able to identify different species by their functional feeding group. The aquatic feeding groups were listed in the lecture, but you have to dig out the ones from the soil readings. Just so you have an idea of some of the terms, they include, saprophage, xylophage, coprophage, necrophage, mycophage, etc. There is quite a bit of reading for this unit, but it is really interesting. When else do you get to read about corpse eating? This concludes Unit